Cryogenic shape and force actuators are required for NASA's Next Generation Space Telescope (NGST). The shape control actuator must provide a small stroke in a rigid structure whereas the force control actuator must provide a controlled force through a small displacement, imposed on a somewhat compliant optical surface. Solenoids can only pull, and thus require a separate return mechanism. Also, since solenoids have moving parts, they are not sufficiently reliable, repeatable, or precise.